This invention relates generally to irrigations sprinklers of the type having an inlet control valve for controlling water inflow to the sprinkler at a regulated pressure. More particularly, this invention relates to an improved inlet control valve designed for improved flush flow passage of grit and debris to correspondingly reduce the risk of trapping grit and debris between a valve member and an associated valve seat.
Irrigation sprinklers of the type having an inlet control valve for controlling water inflow at a regulated pressure are generally well known in the art. Such sprinklers commonly comprise a hollow sprinkler housing or case having a sprinkler mechanism mounted therein. Water under pressure is supplied to the case interior via an inlet fitting located typically at a lower end thereof, resulting in water-powered operation of the sprinkler mechanism to deliver irrigation water through one or more spray nozzles to surrounding vegetation such as grass, shrubs, crops, and the like. The inlet control valve is mounted generally at the inlet fitting and includes a valve member movable between closed and open positions relative to a valve seat for respectively preventing and permitting water inflow to the sprinkler. In the open position, the clearance between the valve member and the valve seat is modulated so that water is supplied to the sprinkler mechanism at a regulated and preferably substantially constant pressure, to achieve a predictable and repeatable delivery of irrigation water to the surrounding terrain. In one common design, the inlet control valve is adapted for automated remote control operation by means of a solenoid powered pilot valve actuator or the like, whereby a plurality of irrigation sprinklers may be employed in an irrigation system and turned on and off from a remote master control station to achieve individually timed watering cycles.
Exemplary irrigation sprinklers equipped with a pressure regulating inlet control valve are shown and described in U.S. Pat. No. 4,637,548; 5,871,156; and 5,899,386. Exemplary pilot valve actuators for opening and closing a control valve, and for operating the open control valve to maintain a substantially constant downstream regulated pressure, are shown and described in U.S. Pat. Nos. 4,081,171 and 4,226,259. Commercially available irrigation sprinklers having pressure regulated inlet control valves include the Rain Bird 47/51 impact drive series and the Rain Bird 900/950 rotor drive series sprinklers, marketed by Rain Bird Sprinkler Mfg., Corp., of Glendora, Calif.
The specific clearance between the open valve member and the associated valve seat of the pressure regulated inlet control valve is a function of the water supply pressure at the upstream side of the valve seat as well as the design rate of water flow through the sprinkler during normal operation. In this regard, the clearance spacing can be relatively small, on the order of about 0.010 inch, when the upstream water supply pressure is relatively high in relation to the regulated downstream pressure within the sprinkler case. Similarly, the clearance spacing can be relatively small when the sprinkler is designed to operate at a relatively low water flow rate. Such small clearance between the open valve member and the valve seat increases the likelihood of trapping small particles of dirt and debris present in the water supply source. Such entrapment of dirt and debris at the valve seat, particularly upon subsequent movement of the valve member to the closed position, can result in damage to sealing surfaces and thus contribute to water leakage through the sprinkler case when the sprinkler is otherwise turned off. This water leakage creates a soggy ground condition surrounding the sprinkler and thereby exposes grass and other vegetation within this soggy zone to over-watering and to potential physical damage when subjected to foot or vehicle traffic.
Another problem encountered with such irrigation sprinklers relates to initial pulsing or oscillation of the valve member when the sprinkler is initially turned on. More particularly, during operating conditions as described above wherein the steady state clearance between the valve member and the valve seat is relatively small, the valve member tends initially to move beyond the desired clearance position when the sprinkler is turned on. The inlet control valve responds to such over-opening by moving the valve member back toward the valve seat. Such back and forth oscillation of the valve member can continue through several cycles before the desired steady state clearance position is reached to achieve the desired steady state regulation of water pressure. During this initial oscillatory or pulsating phase, the valve member can physically contact the valve seat with a sufficient force to present a risk of damage to the valve member or valve seat, wherein such damage can also result in undesired water leakage through the sprinkler case when the sprinkler is turned off.
The present invention is directed to an improved inlet control valve for use in an irrigation sprinkler to provide close regulation of water pressure, wherein the improved inlet control valve incorporates means for insuring valve member movement to an open position with a substantial clearance relative to an associated valve seat, and further wherein the valve member is resistance to oscillatory displacement when the sprinkler is turned on.